The invention relates to a two speed accessory drive mechanism which is capable of rotating a plurality of devices at one of two predetermined speeds. More particularly the invention relates to a two speed accessory drive comprising an input unit driven by a driving member such as an engine crankshaft and further includes an output unit separated from the input unit. Both the input and output units are positioned remotely from the driving member for driving the accessories.
Engines utilize a plurality of accessories such as a power steering pump, water pump, air pump and air conditioner. It is well known that such accessories generate a parasitic drag upon the engine thus reducing its overall efficiency. It is well known that by providing a device such as a two speed accessory drive to drive these accessories the parasitic loss is reduced, fuel ecomony and acceleration performance increased and the longevity of the accessories increased. Typically, the two speed accessory drive is substituted for the engine crankshaft pulley. Such prior drives have utilized planetary gear sets whereby either the sun gear, ring gear or planetary carrier is periodically fixed from rotating thereby causing the planetary gear set to rotate an output member at one of two predetermined speeds. Such planetary gear accessory drives exhibit an audible whine and are relatively long and bulky in order to accommodate the internal gearing mechanisms. With the advent of transversely mounted engines there is not sufficient room in the engine compartment to accommodate these prior direct mounted engine driven drives.
It is an object of the present invention to provide a quietly operating, efficient two speed accessory drive mechanism. A further object of the present invention is to provide such a mechanism which is capable of being remotely positioned from the engine crankshaft pulley such that the drive may be utilized with transversely mounted engines. Accordingly, the invention comprises: A two-speed accessory drive having a high speed or engaged and a low speed or disengaged mode of operation comprising: a driving member, an input unit remotely positioned relative to the driving member, a first belt linking the driving member to the input unit for driving or rotating same, and an output unit remotely positioned relative to the driving member and the input unit. The input unit comprises a input pulley driven by the first belt and a first pulley driven by the input pulley. The output unit comprises a second pulley driven by the first pulley. The diameters of the first and second pulleys are chosen to drive the second pulley at a speed greater than the speed of the input pulley. A third pulley is remotely positioned from the driven by the second pulley. The drive further includes a friction clutch rotationally moved by the second pulley and means for engaging and disengaging the friction clutch to and from the third pulley. The input unit further includes a fourth pulley and overrunning clutch means supporting the fourth pulley relative to the input pulley for driving the fourth pulley at the speed of the input pulley and for permitting the fourth pulley to overrun the speed of the input pulley during instances when the friction clutch is in engagement with the third pulley. The fourth pulley is drivingly connected to the third pulley. The diameters of the third and fourth pulleys are related such that when the friction clutch is disengaged from the third pulley, the third pulley is driven at a speed lower than the speed of the second pulley and when the friction clutch is engaged to the third pulley, the third pulley is driven at the higher speed of the second pulley.
Many other objects, features, purposes and advantages of the invention will be clearer from the detailed description of the drawings.